To attempt the formulation and specification of mechanisms of enzyme catalysis and macromolecule-ligand interactions in terms of chemically and physically distinguishable intermediates. The enzymes will usually be employed in concentrations of the same order as those of the substrates with which they interact, and the changes in both enzyme and substrate monitored by appropriate rapid reaction recording methods. The reactions will be initiated by flow, relaxation, or combined flow relaxation methods, and absorbance, fluorescence, and polarization changes followed.